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  Bruc, L.; Dittrich, T.; Dermenji, L.; Gurieva, G.; Vatavu, S.; Curmei, N.; Guc, M.; Sherban, D.A.; Simashkevich, A.V.; Schorr, S.; Lux-Steiner, M.C.; Rusu, M.; Arushanov, E.: Surface Photovoltage in Thin Films of Cu₂ZnSn(S_xSe₁-x)₄ Obtained by Spray Pyrolysis. In: 31st European Photovoltaic Solar Energy Conference and Exhibition 2015 : 14th - 18th September 2015, Congress Center Hamburg, HamburgMunich: WIP, 2015. - ISBN 3-936338-39-6, p. 1358-1361

10.4229/EUPVSEC20152015-3DV.3.30

Abstract:
Spectral and time dependent surface photovoltage (SPV) measurements were performed on Cu2ZnSn(SxSe1-x)4 (CZTSSe) thin films prepared on ITO/glass substrates by spray pyrolysis at ambient atmosphere from aqueous solutions and subsequent selenization of Cu2ZnSnS4 (CZTS) layers. The morphology, stoichiometry and phases of the crystalline thin films were studied by electron microscopy, energy dispersive x-ray analysis and xray diffraction, respectively. The CZTSSe thin films show mostly the kesterite type CZTSSe phases and are slightly copper deficient. The Se/(S+Se) ratio amounted to about 0.27. The onset energies of SPV signals were observed at about 1.0 and 1.5 eV. The transition at 1.0 eV can be attributed to the SnSe secondary phase with an indirect band gap of 0.90 eV. The energy of 1.5 eV corresponds to the band gap of the CZTSSe with about 25 % of Se content. A slow relaxation process and a change of the sign set on at photon energies above 1.5 eV. Results are discussed in relation to the phase analysis.